The invention relates to a rotary vacuum pump.
Rotary vacuum pumps comprise a suction chamber arranged in a housing. Within the housing, a rotor is eccentrically arranged. Normally, the rotor has two or more sliding vanes connected thereto which are arranged in vane slots. During rotation, the sliding vanes will be pressed against an inner wall of the suction chamber under the effect of the centrifugal force. For generating a vacuum, a suction opening of the rotary vacuum pump is connected to the space wherein the vacuum is to be generated. Due to the eccentricity of the rotor and the varying size of the chambers formed between the sliding vanes, the medium will be conveyed through the discharge channel. For lubrication purposes and also in order to guarantee a good sealing of the sliding vanes on the inner wall of the suction chamber, there always exists a certain quantity of oil for generating an oil film in the suction chamber. Since, for this reason, the discharged medium is mixed with oil, the discharge channel normally extends from the suction chamber into an oil chamber.
In case of a sudden stoppage of the rotary vacuum pump, e.g. due to an impact, this has the consequence that the suction chamber will be filled with oil via the lubricant supply. This will cause an increased moment of rotation and an increased development of noise when the pump is started the next time. Because of the increased moment of rotation, it may happen that the sliding vanes are damaged. Further still, a risk exists that oil could enter the chamber which is to be subjected to a vacuum, and thus could cause damage therein. It is therefore required that, after a stop, the suction chamber of the rotary vacuum pump is brought to atmospheric pressure so as to avoid an inflow of lubricant. To obtain this effect, it is known to provide a bore which is equipped with a closure means and is connected to the suction chamber. This is a relatively complex measure, involving the provision of a separately controllable closure means which must fulfill high requirements regarding its leak-tightness. Further, in cases such as a power fall-out, proper control of the closure means is not guaranteed anymore.
It is an object of the invention to provide a rotary vacuum pump wherein a filling of the suction chamber is prevented by constructionally simple measures.